The method relates to a method for monitoring a battery in a vehicle, which comprises multiple battery cells. The method further relates to a computer program, a battery system and a vehicle which are equipped to carry out the method.
Electronic control devices are increasingly used today in the automotive field, for example for the motor management system, the antilock braking system (ABS) or the airbag. The design and development of batteries which comprise a plurality of battery cells consolidated in battery modules and of the associated battery management system is essential for electrically driven vehicles. In this context, the battery management system comprises a control device with software for monitoring and controlling the battery functionality.
Depending on the requirements and the available installation space, the topologies of the battery are very diverse with regard to the number of battery cells, battery modules and sensors. In the European patent publication EP 2 503 665 A1, a voltage supply system comprising an electrical storage unit is, for example, described. During operation of the electrical storage unit, said unit is charged or, respectively, discharged, wherein the profile of a cell voltage follows a charging or, respectively, discharging curve.
Typical battery management systems ensure a safe and reliable performance of the battery. Said systems monitor and control currents, voltages, temperatures, insulation resistances and other operating parameters which characterize the condition of the battery cells, the battery modules and therefore the battery. With the aid of the operating parameters, management functions can be implemented which increase the service life, the reliability and the safety of the battery.
The German patent specification DE 10 2009 036 083 A1 describes a method for controlling operating states of a battery on the basis of an assessment which is obtained with the aid of approximation functions. In so doing, the assessment consists of ageing curves which were obtained by measuring first operating states. By interpolating between these measured values, assessments are then obtained for second operating states. The approximation functions are functions of the operating state variables and further parameters, wherein the parameter values are stored in a storage unit.
In the prior art, different options are known for storing data in a battery system. In the German patent specification DE 10 2008 041 103 A1, a detection device is described for determining a state of charge of an electrical storage unit in the motor vehicle. The state of charge is thereby determined using a characteristic curve which describes an electrical loading of storage cells as a function of the individual cell voltage. The characteristic curve for ascertaining the load capacity of the battery is stored in a data storage unit.
A battery system which comprises multiple battery cells in battery modules is known from the European patent specification EP 2 485 293 A1. The battery system further comprises integrated circuits which, inter alia, carry out a diagnosis of the cells of the battery modules. The battery system further comprises a non-volatile storage unit, in which data regarding the usage behavior of the battery modules including the maximum voltage or the maximum current of the battery modules and a history of the battery modules are stored. In addition, such stored usage information can describe the extent of the use in which certain standards were exceeded. The maximum and the minimum supply voltage can also be stored. In addition, the maximum load current and the maximum charging current can further be stored.
It is important for reasons of safety and reliability that a history of the use of the battery is kept. This comprises, for example, usage information about the battery in certain temperature ranges at certain voltages. Within the scope of warranty claims, stored usage information can be read from a non-volatile storage unit of the control device and can be used to evaluate the use of the battery. Thus, detailed information about the use of the battery is available during the service life thereof.
In order to also retrospectively reconstruct the use of the battery, i.e., for example, in the event of failure of the battery, it is necessary to deposit operating parameters of said battery in a non-volatile storage unit. Over the service life of a battery, so many operating parameters are however accumulated that the storage capacity is quickly exceeded. For that reason, there is a continuing interest for structuring the storage of operating parameters as efficiently and sustainably as possible; so that, on the one hand, the storage capacity is not overloaded and, on the other hand, the use of the battery can be reconstructed over the service life thereof.